The present invention relates generally to lighting fixtures activated by passive infrared motion detectors and is particularly directed to such lighting fixtures that include floodlights or spotlights that may be aimed in desired directions.
A passive infrared (PIR) motion detector is a device used to turn on a light when a person or motor vehicle enters a monitored area. Such devices are often used with outdoor residential lighting, for example, to illuminate an area as a person approaches or to illuminate a driveway as a car approaches. The PIR motion detector functions by sensing heat in the form of infrared radiation emanating from a person or similarly warm object as the person or object enters or moves about in the field of view of the detector. When the motion detector detects an appropriate heat impulse characteristic of a moving heat source, it provides an electrical signal to activate the light. The motion detector commonly keeps the light on for a pre-set duration after motion has been detected. Thus, for example, when a person enters the motion detector's field of view, a light comes on and remains on typically for five, ten or fifteen minutes at the selection of the user. The light is then automatically extinguished at the end of the pre-set period unless further motion is detected.
The typical motion-detector activated floodlight includes a supporting base that is mounted on a wall or that is soffit mounted, for example, on a side wall of a house, and one or two floodlight holder assemblies that are mounted on the base. The floodlight holder assemblies, which are sometimes referred to simply as lamp holders, are typically connected to the base by an arm that is pivotally connected to the back end of the lamp holder. The pivoting connection permits the lamp to be aimed in a desired direction. The motion detector is contained in a separate housing that is also connected to the base by a pivoting connection so that it too may be aimed in a desired direction.
A problem with false activations can arise, however, if the floodlights and the motion detector are aimed so that even a small portion of a lamp holder assembly falls within the field of view of the motion detector. In this case the heat from a lamp holder and lamp that has just been extinguished can trigger the motion detector to re-energize the lamp. It is common practice for the motion detector to include electronic circuitry that disables the motion detector for a very brief re-set period when the light is extinguished to permit the light to cool down before the motion detector is re-armed. When a portion of the floodlight housing protrudes into the field of view of the motion detector, however, the usual re-set period is not long enough. Increasing the duration of the re-set period to allow the lamp to cool sufficiently would lead to an unacceptably long time during which the motion detector would be disarmed. In the past motion-detector controlled floodlights have avoided this problem primarily by mounting the motion detector housing sufficiently far from the floodlights. This is typically achieved by mounting the detector housing on a support arm that juts out and/or down from the base far enough to avoid interference from the floodlights. The result is a lighting fixture that is unduly large with lanky arms (for the motion detector and the lamp holders) that dominate the overall appearance of the fixture and that limit the range of aesthetic designs for such a fixture.